1. Technical Field
The disclosure relates to an ultrasound diagnosis apparatus configured to generate an ultrasound image based on an ultrasound signal obtained by an ultrasound probe that transmits ultrasound to a subject and receives the ultrasound reflected from the subject. The disclosure also relates to a method for operating the ultrasound diagnosis apparatus, and a computer-readable recording medium.
2. Related Art
In an ultrasound diagnosis apparatus that generates an ultrasound image based on an ultrasound signal obtained by an ultrasound probe that transmits ultrasound to a subject and receives the ultrasound reflected from the subject, there is a known technique of calculating an attenuation rate of the ultrasound inside the subject (for example, refer to JP 2010-82230 A). In this technique, a Gaussian pulse is transmitted from an ultrasound probe to a subject, and along with this, performs quadrature detection onto a reception signal output from the ultrasound probe to obtain a phase ϕ(t) indicating a phase of an ultrasound echo, so as to obtain second-order differential value d2ϕ/dt2 for time t from which a speckle component has been removed. In JP 2010-82230 A, an attenuation rate α is calculated using a relational equationd2ϕ/dt2=2πα×(Δw)2×v  (1)
satisfied by attenuation per unit distance (attenuation rate in JP 2010-82230 A) α, the second-order differential value d2ϕ/dt2, sound velocity v, and known bandwidth Δw (π represents the ratio of the circumference of a circle to its diameter). JP 2010-82230 A merely describes acquisition of the sound velocity v using another technique and does not disclose details of the technique.
There is a known ultrasound diagnosis apparatus that differentiates a noise region as a low S/N region and displays this information on the low S/N region with an attenuation image as an image based on the attenuation rate (for example, refer to JP 2013-5876 A). This technique stops transmission of ultrasound under a condition equal to a case of transmitting and receiving an ultrasound signal having a center frequency of 4 MHz and generates a noise image based on a noise signal received from individual positions of the subject. During the examination, brightness of the noise image is compared with brightness of a B-mode image with 4 MHz, a pixel having the same brightness is extracted as a low S/N region, and then, information on the pixel on this low S/N region and the attenuation image generated separately are displayed on a monitor.